How many stories have you heard of a burst pipe and a flooded house when someone returned from vacation?  Every insurance adjuster has heard hundreds of these so before going on vacation, turn off the main valve.  In less than a minute, you can eliminate the most common cause of home damage. The main shutoff is typically in the basement.  If these haven't been "exercised" in awhile, you may encounter a few drips when you first turn it off.  Wait a few minutes to be sure the drips have stopped completely